The Xon evolved on the continent of Xonos, separate from the distant continent on which the Centauri evolved and it was not until one or both civilisations developed the technology to cross the oceans that they became aware of one another.[3][4]

Described by later generations of Centauri as "fierce warrior creatures", when the Xon finally did meet the Centauri, the two races began competing with one another for land and resources, culminating in a long and fierce war for control of the planet that became known as the War of 20 Million Deaths.[5][2][6]
The Centauri eventually prevailed, wiping out the Xon completely in 1258 and the new Centauri Republic was founded.[7] The First Emperor of the Republic is recorded in Centauri history as "Subduer of the Xon".[8]

Centuries later, Centauri religious ceremonies still commemorate the victory of the Centauri over the Xon.[2]